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Concise Definitions of Free Radical & Oxidative Stress
What are free radicals?
Free radicals (often referred to as radicals) are atoms, molecules, or ions of unpaired electrons. Free radicals are not byproducts in general. In theoretical chemistry, free radicals are called “open shell” species, while “closed shell” is the term used for species that have only paired electrons. The term “open shell” is more accurate scientific term for free radicals. Free radicals are not limited to species of odd number of electrons, but also include some those of even but unpaired electrons. By convention, metals, metal ions, and their complexes of unpaired electrons are not free radicals. Any inorganic gases or organic species of unpaired electrons are free radicals.
Many antioxidant sellers make funny &
wrong descriptions of free radicals & oxidative stress
Our PhD scientists noticed a huge number of wrong and funny statements of free radicals by many OPC antioxidant sellers and marketers in the internet. Here are a few examples as quoted:
"Free radicals are simply electrons that are no longer attached to atoms. Instead of circling the nucleus of an atom (much like the earth circles the sun), free radicals are both free and radical enough to go careening through our cells, inflicting damage as they go." -:) -:) -:)......
This funny sentence was copied over and over again by many OPC antioxidant sellers to explain the oxidative stress. We searched Google using the quoted phrase "Free radicals are simply electrons that are no longer attached to atoms", and found 312 web pages on 3/25/2010, and 231 web pages on 10/3/2010.
"Free radicals are atoms or groups of atoms with an odd (unpaired) number of electrons and can be formed when oxygen interacts with certain molecules." -:)
"Some molecules are unstable. They do not have an even number of electrons, so they are always searching for an extra electron they can 'steal' to become stable." -:(
"Free radicals are unpaired single electrons, violently reactive like a rapist seeking sex, very damaging physically and emotionally..."-:) -:) -:) -:) -:)......
"Free radicals are harmful byproducts of metabolism and exposure to environmental pollutants” -:(
“Free radicals are extremely unstable and highly destructive oxygen molecules” -:(
......
These wrong statements appear in some websites highly ranked by search engines based on popular key words: "free radical", "oxidative stress", "antioxidant", etc. Most website content writers for professional search engine optimization (SEO) services do not have appropriate scientific knowledge, so that they simply write or copy wrong statements on science, and keep optimizing the wrong staff onto the top spot of search engines. That is exactly the distorted human civilization in the internet era.
Oxygen molecule is a biradical, and hence radicals
The oxygen molecule (O2 or O-O) itself is free radicals or a bi-radical, with two unpaired electrons. In theoretical chemistry, this ground state bi-radical is called “triplet” oxygen. That is, the electron configuration of the molecule has two unpaired electrons occupying two degenerate molecular orbitals with the same spin orientation (up-up or down-down). “Triplet” means 3 different quantum states of the total magnetic property projected along the direction of an external magnetic field.
A few people argue that oxygen molecule is not a free radical as it is not reactive enough to be radical, with which our PhD scientists don't agree. It is generally accepted that oxygen molecule is a biradical at the level of theoretical chemistry. Any one may search Google or Yahoo, using quoted phrases "oxygen molecule is a free radical" or "oxygen molecule is a biradical".
The unpaired electrons cause radicals to be highly reactive chemically in general. But the reactivity of radicals varies widely. Organic free radicals are almost always very reactive and short-lived, although organic chemists have made a few examples of special organic free radicals that are stable at room temperature. Therefore, the reactivity is not a criterion for the classification of free radical.
Why an oxygen molecule (O2) has 2 unpaired electrons?
Non-Free radical molecules of higher stability have even number of electrons to form electron pairs, - closed-shell system as called in theoretical chemistry. In the language of classical physics, each electron pair means that the 2 electrons spin in 2 opposite directions (anti-parallel) so that the magnetic forces due to the spins of charged particles (electrons) are complementary to each other. In the language of non-classical quantum physics, there are actually no electron pairs at all. All electrons exist as electron cloude and the net magnetic properties of spins are cancelled out.
But some molecules of even number of electrons may be free radicals, as caused by the interplay of complex electromagnetic forces under specific circumstances. An oxygen molecule of even number of electrons is a biradical with 2 unpaired electrons. This was first established by experimental observation that the ground state of O2 exhibited magnetic properties of 2 electrons spinning in the same direction in the presence of a magnetic field. The classical theories of electronic structure could not explain this. But modern quantum mechanical calculations can rationalize this easily, showing the 2 outer shell electrons occupy 2 degenerate orbitals with the same spin direction. The "quantum effect" is a very tricky term in science, so that even some greatest physicists such as Plank, Gell-Mann and Feynman (3 Nobel Laureates in physics) expressed the "frustration" in some ways. Murray Gell-Mann described quantum mechanics as "that mysterious, confusing discipline which none of us really understands but which we know how to use". Richard Feynman said, “I think I can safely say that no-one understands quantum mechanics… Do not keep asking yourself, if you can possibly avoid it, …”
Do oxygen molecules cause oxidative stress?
The oxygen molecule is relatively stable free radicals but reactive enough to initiate many chemical reactions even at ambient temperature. It is equivalent to 2 free radicals. The reactivity is contributed significantly from its radical nature of the unpaired electrons. Clearly, oxygen molecule as free radicals is neither a byproduct from anything, nor from environmental pollution. It is an essential substance for life. In human body, oxygen is carried within vehicles - oxygen-carrying proteins such as myoglobin, hemoglobin, hemerythrin, and hemocyanin. Normally, these vehicles protect oxygen molecules from directly contacting with any reducing agent and from being harmful during transportation, and send oxygen to pre-defined destination for energy-producing metabolism activities. The di-atomic oxygen molecule (O2) as a biradical causes neglectable oxidative stress inside the body. It is energy-producing event generates free radical byproducts such as oxygen radical or peroxide, which cause oxidative stress and have to be dealt with antioxidants such as OPCs.
Oxidative stress of O2 in the air may lead to skin damage due to its oxidizing ability and contributes the skin ageing and wrinkling in a very slow and chronical way. The oxidative stress on skin may be minimized if effective antioxidants are taken in the long-term.
The simplest radical
The simplest free radical is a hydrogen atom (H•). The single and unpaired electron is denoted as •. A hydrogen molecule consists of 2 hydrogen atoms that are connected by sharing a pair of electrons between them, forming a chemical bond (H2, H:H or H-H). A hydrogen molecule has an electron pair, and therefore, it is not a free radical. When hydrogen gas is irritated with UV light in an isolated environment (without oxygen), a hydrogen molecule (H-H) may be broken evenly (homolytic cleavage) to give two hydrogen atoms or two free radicals H2 → 2H•. The two free radical hydrogen atoms could combine to go back to the hydrogen molecule: 2H•→ H2. However, the chance for the two exactly same atoms to meet and to form a di-atomic molecule again is almost zero, simply because each of the 2 free radicals is too reactive to give their partner a chance. Each hydrogen atom free radical grabs almost anything it collides with.
Free radicals generated in 3 ways
There is no absolute answer to origin of free radicals in the universe, just like it is hard to answer the origins of life, universe, etc.. But it is not hard to answer the question how free radicals are generated in the ecosystem on the earth. Chemically, there are about 3 ways free radicals are generated:
1) Photon-induced formation of free radicals.
This is the major and more significant way of free radical generation than the other 2 ways to be discussed in the next. Free radicals are highly energetic chemical species in general, and require energy for their formation. The rich energy source for the free radical formation is the sun light – photons. The plant photosynthesis generates the most abundant free radicals – oxygen molecules via a variety of oxygen free radical intermediates. This way of free radical generation is crucial for the existence of human and other animal life on the earth. The sun light also causes diverse free radical formation in the atmosphere. The sun light can cause the split of oxygen molecule (diatomic molecule) into 2 oxygen atoms (or 2 radicals) in the upper atmosphere. Each oxygen free radical atom in the atmosphere may combine with an oxygen molecule to form ozone (another highly energetic chemical species). Ozone gas derived from oxygen free radicals forms an ozone layer in the upper atmosphere, protecting human life on the earth from the damages of UV light of the sun. How can one say that "free radicals are harmful byproducts of metabolism and exposure to environmental pollutants”?
2) Free radical chain reactions to new free radicals from existing free radicals.
In the human body, free radicals are generated from other existing free radicals (the oxygen molecule). The exception is that cancer radiation therapy also generates free radicals in the body.
The oxygen molecule is converted to hydrogen peroxide in the electron transfer processes in the synthesis of ATP (see the next section). The resulting hydrogen peroxide contains a highly energetic oxygen-oxygen bond, and may be further converted to free radicals by homolytic cleavage of the oxygen-oxygen bond, or by another electron transfer. Oxygen free radicals and hydrogen peroxide in the human body are called reactive oxygen species (ROS) in biology.
3) Thermal chemical reactions generate free radicals.
Free radicals can be generated at high temperature as they require high energy. An example is free radical formation when saturated alkanes are heated at high temperatures to break the carbon-carbon and/or carbon-hydrogen chemical bonds in an isolated vessel without oxygen. Free radicals are also rich as the reactive intermediate in combustion, which are, however, mainly from free radical chain reactions involving oxygen. Free radicals may be generated at low temperature or room temperature, only from chemicals that have a highly energetic chemical bond. In some chemical labs, some free radical initiators (e.g. peroxybenzoic acid) belong to this kind. An example of high energetic chemical bond is oxygen-oxygen bond, which can be broken easily to form 2 free radicals. Another example is diaza type compound: 2 nitrogen atoms are connected together within an organic molecule. Upon slight heating, the 2 nitrogen atoms are broken from the rest of the molecule, forming a nitrogen molecule and 2 free radicals within the rest of organic molecule(s).
Physics of energy storage in the ecosystem
Energy is required for cells to perform many fundamental tasks: to drive biochemical reactions that would not occur automatically; to transport needed materials across membranes; and to carry out mechanical work, such as moving muscles. Fat, proteins and carbohydrates are the actual energy storages in the living systems. More concisely, the energy storage is a conjugated system of organic compounds and oxygen molecules. The photosynthesis in plants stores solar energy by making organic compounds from carbon dioxide and water, releasing oxygen gas. One of the physical consequences in the plant photosynthesis is that the electrons are relocated from the space of more positive electronic potential near oxygen to the space of less positive electronic potential near carbon or hydrogen. The potential energy of electrons are therefore elevated. The electron transfer process requires the involvement of free radicals - chemical species of unpaired electrons.
ATP as the essential energy transfer vehicle in living systems
When energy is needed by the cell, the energy is converted from storage molecules to the energy carrier molecules ATP (adenosine-5’- tri-phosphate). This energy transfer process requires oxygen molecules to oxidize organic nutrients such as carbohydrates, fatty acids, amino acids to generate carbon dioxide, releasing energy that can be utilized in the formation of ATP.
ATP molecule contains three phosphate groups, and it is formed by ATP synthase from inorganic phosphate and adenosine diphosphate (ADP). The energy required for the ATP formation comes from either photophosphorylation in the plants, or oxygen-related oxidative reactions during cellular respiration. ATP is a multifunctional nucleotide used in cells as a coenzyme. "Molecular unit of currency" is an often used term for ATP in the intracellular energy transfer. ATP, transporting chemical energy within cells for metabolism, is used by enzymes and structural proteins in many cellular processes, including biosynthetic reactions, motility, and cell division. In the metabolic processes that requires ATP, ATP releases energy and is converted back into its precursor ADP. This is a continuously recycling process in living systems.
Normal bio-metabolism generates harmful free radical byproducts -
reactive oxygen species (ROS) and causes oxidative stress
The oxidation of fat, proteins and carbohydrates by oxygen (O2) generates bio-energy (ATP), carbon dioxide (CO2) and water (H2O) in the normal bio-metabolism. The physical essence of these redox reactions is that electrons are transferred from locations of high potential energy in fat, proteins and carbohydrates to locations of low potential energy near or in oxygen, releasing the energy for the formation of ATP – the storage molecule of bio-energy.
The driving force for this bio-metabolism is that the reactive oxygen molecule as a biradical that has affinity for electrons. When oxygen molecule (O2) accepts one electron, it is converted to anionic radical (O2-•), which can catch a proton (H+) in the medium and is converted instantly to hydrogen peroxide radical (HOO•). The hydrogen peroxide radical (HOO•) gets another electron to form hydrogen peroxide anion (HOO-), which catch a proton in the medium to form hydrogen peroxide (HOOH, or H2O2). Hydrogen peroxide may cleave homolytically to give 2 hydroxy radicals (HO•), or accept one electron to give hydroxide (HO-) and hydroxy radical (HO•). The hydroxide ((HO-) catches a proton instantly in the media to produce a water molecule (H2O). The hydroxy radical (HO•) may accept one more electron to give another hydroxide (HO-), which is again converted to a water molecule instantly by catching another proton in the media.
What is oxidative stress?
Excess free radicals attack and harm the human body
In the normal bio-metabolism process, one molecule of oxygen leads to the formation of 2 molecules of water. If this normal bio-metabolism process could be strictly followed, there wouldn’t be harmful radicals. However, the oxygen radical intermediates and hydrogen peroxide (HOO•, HOOH, HO•) are very reactive, so that they tend to grab or stick to anything they can meet, causing damages. Further, the quantities of these oxygen radical intermediates and hydrogen peroxide are huge. Every oxygen molecule we absorb from breath has to go through the intermediates of oxygen radicals and/or hydrogen peroxide.
Oxidative stress is a general term describing the free radical damages to cells, organs and the living system. The oxidative stress exists when the free radical damages exceed the level that can be managed by the immune system. Oxidative stress can be alternatively described as a physical state in the human body that there is an abnormally high level of reactive oxygen species (ROS).
Human genes encode several functional enzymes – antioxidant enzymes that perform this special task for disposal of the harmful excess oxygen free radicals, battling the oxidative stress. Human genes also encode repairing enzymes that can fix most of the damages derived from free radical - induced oxidative stress. However, oxidative stress often leads to some rare unfixable damages. The accumulation of the damages day-by-day would lead to diseases and/or aging. In the aging process, the activities of the antioxidant enzymes and repairing enzymes decrease, and the oxidative stress gets more and more prevailing, so that ageing process is accelerated.
Inappropriate physical exercises may cause excess free radicals & oxidative stress
Human indeed benefits from physical exercises in many ways, such as increasing muscle and bone strength, changing body shape, losing weight, stimulating blood circulation and metabolism, etc.. However, inappropriate physical exercises may cause harms due to excess oxidative stress - abnormally high level of reactive oxygen species (ROS). The effects of physical exercises are 2-sided. Physical exercises cause the formation of larger than normal quantities of oxygen free radicals in the human body, accelerating the aging process. This is especially true for the middle aged people with decreased activities of antioxidant enzymes and repairing enzymes. Excessive physical exercises cause oxidative stress and accelerated aging.
Oxidative stress as the primary Free radical damage
Free radicals are not always evils in general, and are the normal chemical species that are required in metabolism of life. Without radicals, there wouldn’t be life. Only excess radicals that escaped from the normal metabolism routes via uncontrolled radical chain reactions are harmful to life, and cause oxidative stress, leading to aging, cancer…… Free radical byproducts may be the worst enemy of life. Oxidative stress as the primary Free radical damage may lead to all possible diseases and ageing.
Extent of free radical damages by experts
"Free oxygen radicals, the main type formed in living organisms, have been implicated in recent studies in more than 60 disorders, including heart disease, cancer, Alzheimer's disease, Parkinson's disease, cataracts and rheumatoid arthritis. And according to one of the leading theories on aging, they contribute to the process of becoming old, such as wrinkling of the skin, decline of kidney function and increased susceptibility to autoimmune diseases." New York Times, April 26, 1988.
When Dr. Masquelier, a famous OPC professor from France was asked if there is a relationship between OPC's and cancer, this was his response: "Certain types of cancer form secondary tumors by dissolving material around tissues and cells. These cancer cells produce dissolving enzymes, proteases... and we know that OPC protects proteins against proteases. Breast cancer is a type of cancer that spreads via producing secondary tumors by producing proteases. So to me it seems logical to administer OPC as soon as breast cancer is diagnosed to prevent secondary tumors developing. But also breast cancer is caused for a large part by the destruction of our DNA by free radicals. By protecting DNA, OPC will also protect us indirectly against the risk of cancer." †
It should be noted, however, that these quotes are just some personal opinions from scientists and scholars. There have not been any officially accepted clinical evidence that antioxidants can prevent, cure or treat any diseases, according to the US FDA regulations.
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† These statements have not been evaluated by the US Food & Drug Administration.
FrenchGlory ® isotonic OPC antioxidants are nutritional supplements, not intended to diagnose, treat, care or prevent any diseases.
